The invention relates to a composition for the oxidation dyeing of keratin fibres, especially human keratin fibres such as the hair, comprising, in a medium suitable for dyeing, at least one oxidation base and at least one specific cationic dye as direct dye, as well as to the dyeing process using this composition.
It is known to dye keratin fibres, particularly human hair, with dye compositions containing oxidation dye precursors, in particular ortho- or para-phenylenediamines, ortho- or para-aminophenols and heterocyclic bases, generally referred to as oxidation bases. Oxidation dye precursors, or oxidation bases, are colourless or weakly coloured compounds which, when combined with oxidizing products, can give rise to coloured compounds and dyes by a process of oxidative condensation.
It is also known that the shades obtained with these oxidation bases can be varied by combining them with couplers or colour modifiers, the latter being chosen in particular from aromatic meta-diamines, meta-aminophenols, meta-diphenols and certain heterocyclic compounds.
The variety of compounds used as oxidation bases and couplers allows a wide range of colours to be obtained.
It is also known that direct dyes, i.e., coloured substances which give a coloration in the absence of an oxidizing agent, can be used, in combination with the oxidation dye precursors and the couplers, to further vary the shades obtained and to give them glints.
The vast majority of these direct dyes belong to the family of nitrobenzene compounds and have the drawback, when they are incorporated into dye compositions, of leading to colorations which show insufficient staying power, especially with respect to shampooing.
The so-called xe2x80x9cpermanentxe2x80x9d coloration obtained by these oxidation dyes should, moreover, satisfy a certain number of objectives. The dyes should allow shades to be obtained in the desired intensity and should show good resistance to external agents (light, bad weather, washing, permanent-waving, perspiration, rubbing).
The dyes should also be able to cover grey hair and, finally, they should be as unselective as possible, ie., they should allow only the smallest possible colour differences along the same keratin fibre, which may indeed be differently sensitized, i.e., damaged, between its tip and its root.
The present invention is directed towards proposing novel compositions for the oxidation dyeing of keratin fibres, especially human keratin fibres such as the hair, which produce colorations that are preferably rich in glints while at the same time having good properties of staying power.
Thus, the inventors have discovered that it is possible to obtain novel dyes which are can be both rich in glints and have good staying power by combining:
at least one oxidation base,
at least one cationic direct dye of formula (I) defined below.
This discovery forms the basis of the present invention.
Additional features and advantages of the invention are set forth in the description that follows, and, in part, will be apparent from the description or may be learned from practice of the invention. The advantages of the invention will be realized and attained by the dyeing compositions, processes, and kits particularly pointed out in the written description and claims.
Both the foregoing general description and the following detailed description of the invention are exemplary and explanatory only and are not restrictive of the claimed invention.
A first subject of the invention is a composition for the oxidation dyeing of keratin fibres, especially human keratin fibres such as the hair, comprising, in a medium suitable for dyeing:
at least one oxidation base,
at least one cationic direct dye of formula (I) below:
Axe2x80x94Nxe2x95x90Nxe2x80x94Bxe2x80x83xe2x80x83(I)
xe2x80x83wherein:
A is chosen from structures A1, A2, and A3 below: 
xe2x80x83wherein in said structures A1 to A3:
R1 is chosen from C1-C4 alkyl radicals, a phenyl radical, and phenyl radicals having a substituent chosen from C1-C4 alkyl radicals and halogen atoms chosen from chlorine, bromine, iodine and fluorine;
R2 is chosen from C1-C4 alkyl radicals and a phenyl radical;
R3 and R4, which may be identical or different, are chosen from C1-C4 alkyl radicals and a phenyl radical or together form a benzene ring having at least one substituent chosen from C1-C4 alkyl radicals, C1-C4 alkoxy radicals, and nitro radicals; R3 can also be a hydrogen atom;
R5 and R6, which may be identical or different, are chosen from C1-C4 alkyl radicals and a phenyl radical or together form a benzene ring which is unsubstituted or has at least one substituent chosen from C1-C4 alkyl radicals, C1-C4 alkoxy radicals, and nitro radicals; R5 can also be a hydrogen atom;
R7 and R8, which may be identical or different, are chosen from a hydrogen atom, halogen atoms chosen from chlorine, bromine, iodine and fluorine, C1-C4 alkyl radicals, C1-C4 alkoxy radicals and nitro radicals;
Z is chosen from an oxygen atom, a sulphur atom, and a group NR2, wherein R2 is chosen from C1-C4 alkyl radicals and a phenyl radical;
the ring member L is chosen from xe2x80x94CH, xe2x80x94CR and xe2x80x94N+R9(Xxe2x88x92)r;
the ring member M is chosen from xe2x80x94CH, xe2x80x94CR and xe2x80x94N+R9(Xxe2x88x92)r;
r is an integer equal to 0 or 1;
R is chosen from C1-C4 alkyl radicals;
R9 is chosen from an atom Oxe2x88x92, C1-C4 alkyl radicals, and C1-C4 alkoxy radicals;
Xxe2x88x92 is chosen from an anion preferably chloride, methyl sulphate, ethyl sulphate, acetate, and perchlorate;
xe2x80x83with the provisos that:
in the formula A3, at least one of the ring members L and M is chosen from a group xe2x80x94N+R9(Xxe2x88x92)r;
when R6 is a C1-C4 alkyl radical and Z is a sulphur atom, then R5 is other than a C1-C4 alkyl radical;
when R6 is a C1-C4 alkyl radical and Z is a sulphur atom and when one of the radicals R10 and R11, defined below, is a hydrogen atom, then R5 is other than a hydrogen atom;
when R9 is Oxe2x88x92, then r=0;
when L or M is a radical xe2x80x94N+R9(Xxe2x88x92)r wherein R9 is a C1-C4 alkyl radical and r=1, then at least one of the radicals R7 and R8 is other than a hydrogen atom;
when L is a radical xe2x80x94N+R9(Xxe2x88x92)r, then M is chosen from a group xe2x80x94CH and CR;
when M is a radical xe2x80x94N+R9(Xxe2x88x92)r, then L is chosen from a group xe2x80x94CH and CR;
when Z is a group NR2 wherein R2 is a C1-C4 alkyl radical, then at least one of the radicals R1, R5 and R6 is other than a C1-C4 alkyl radical;
when Z is a sulphur atom and R1 is a C1-C4 alkyl radical and when one of the radicals R10 and R11, defined below, is a hydrogen atom, then R5 and R6 cannot together form an unsubstituted benzene ring;
B is chosen from:
(a) a group of structure B1 below: 
xe2x80x83wherein in structure B1,
R10 is chosen from a hydrogen atom, halogen atoms chosen from chlorine, bromine, iodine and fluorine, C1-C4 alkyl radicals, C1-C4 alkoxy radicals, a hydroxyl radical, xe2x80x94NHR13 groups, xe2x80x94NR14R15 groups, xe2x80x94NHCO(C1-C4)alkyl groups and a nitro, or forms with R11 a 5- or 6-membered carbon ring or a ring containing at least one hetero atom chosen from nitrogen, oxygen and sulphur;
R11 is chosen from a hydrogen atom, halogen atoms chosen from chlorine, bromine, iodine and fluorine, C1-C4 alkyl radicals, and C1-C4 alkoxy radicals or forms with R12 or R13 a 5- or 6-membered carbon ring or a ring containing at least one hetero atom chosen from nitrogen, oxygen and sulphur;
R12 is chosen from a hydrogen atom, a hydroxyl radical, xe2x80x94NHR13 radicals, and xe2x80x94NR14R15 radicals;
R13 is chosen from a hydrogen atom, C1-C4 alkyl radicals, C1-C4 monohydroxyalkyl radicals, C2-C4 polyhydroxyalkyl radicals, and a phenyl radical;
R14 and R15, which may be identical or different, are chosen from C2-C4 alkyl radicals, C1-C4 monohydroxyalkyl radicals, and C2-C4 polyhydroxyalkyl radicals; and
(b) a 5- or 6-membered nitrogenous heterocyclic group, a 5- or 6-membered nitrogenous heterocyclic group comprising at least one additional hetero atom chosen from oxygen and sulphur and/or at least one carbonyl group, wherein said heterocycles are unsubstituted or have at least one substituent chosen from C1-C4 alkyl, amino and phenyl radicals.
Among the said 5- or 6-membered nitrogenous heterocyclic groups featured above, preferred compounds include groups of structure B2 below: 
wherein in structure B2:
R16 and R17, which may be identical or different, are chosen from a hydrogen atom, C1-C4 alkyl radicals and a phenyl radical;
Y is chosen from 
and 
and
n is an integer equal to 0 or 1.
The cationic direct dyes of formula (I) above are known compounds of the prior art and are described, for example, in patent application FR-A-2,140,205 and its Certificates of Addition, as well as in patent application FR-A-2,189,006, the disclosures of which are specifically incorporated by reference herein.
The dye composition according to the invention can give intense, chromatic colorations which show little selectivity and excellent properties of resistance both with respect to atmospheric agents such as light and bad weather, and with respect to perspiration and the various treatments to which hair may be subjected. These properties can be particularly noteworthy with respect to chromaticity.
Another subject of the invention is a process for the oxidation dyeing of keratin fibres using this dye composition.
In the compounds of formula (I) above, the C1-C4 alkyl and alkoxy radicals are preferably chosen from the methyl, ethyl, butyl, methoxy and ethoxy radicals.
The nature of the oxidation base(s) used in the dye composition according to the invention is not a critical factor. They can be chosen, for example, from para-phenylenediamines, double bases, para-aminophenols, ortho-aminophenols and heterocyclic oxidation bases.
Among the para-phenylenediamines which can be used as oxidation bases in the dye compositions according to the invention, examples include the compounds of formula (II) below, and the addition salts thereof with an acid: 
wherein:
R18 is chosen from a hydrogen atom, C1-C4 alkyl radicals, C1-C4 monohydroxyalkyl radicals, C2-C4 polyhydroxyalkyl radicals,(C1-C4)alkoxy(C1-C4)alkyl radicals, C1-C4 alkyl radicals substituted with an entity chosen from nitrogenous groups, a phenyl group and a 4xe2x80x2-aminophenyl group;
R19 is chosen from a hydrogen atom, C1-C4 alkyl radicals, C1-C4 monohydroxyalkyl radicals, C2-C4 polyhydroxyalkyl radicals,(C2-C4)alkoxy(C1-C4)alkyl radicals and C1-C4 alkyl radicals substituted with a nitrogenous group;
R20 is chosen from a hydrogen atom, halogen atoms such as chlorine, bromine, iodine and fluorine atoms, C1-C4 alkyl radicals, C1-C4 monohydroxyalkyl radicals, C1-C4 hydroxyalkoxy radicals, acetylamino(C1-C4)alkoxy radicals, C1-C4 mesylaminoalkoxy radicals and carbamoylamino(C1-C4)alkoxy radicals,
R21 is chosen from hydrogen and halogen atoms and C1-C4 alkyl radicals.
Among the nitrogenous groups of formula (II) above, examples include amino, mono(C1-C4)alkylamino, di(C1-C4)alkylamino, tri(C1-C4)alkylamino, monohydroxy(C1-C4)alkylamino, imidazolinium and ammonium radicals.
Among the para-phenylenediamines of formula (II) above, examples include para-phenylenediamine, para-tolylenediamine, 2-chloro-para-phenylenediamine, 2,3-dimethyl-para-phenylenediamine, 2,6-dimethyl-para-phenylenediamine, 2,6-diethyl-para-phenylenediamine, 2,5-dimethyl-para-phenylenediamine, N,N-dimethyl-para-phenylenediamine, N,N-diethyl-para-phenylenediamine, N,N-dipropyl-para-phenylenediamine, 4-amino-N,N-diethyl-3-methylaniline, N,N-bis(xcex2-hydroxyethyl)-para-phenylenediamine, 4-amino-N,N-bis(xcex2-hydroxyethyl)-2-methylaniline, 4-amino-2-chloro-N,N-bis(xcex2-hydroxyethyl)aniline, 2-xcex2-hydroxyethyl-para-phenylenediamine, 2-fluoro-para-phenylenediamine, 2-isopropyl-para-phenylenediamine, N-(xcex2-hydroxypropyl)-para-phenylenediamine, 2-hydroxymethyl-para-phenylenediamine, N,N-dimethyl-3-methyl-para-phenylenediamine, N,N-(ethyl-xcex2-hydroxyethyl)-para-phenylenediamine, N-(xcex2xcex3-dihydroxypropyl)-para-phenylenediamine, N-(4xe2x80x2-aminophenyl)-para-phenylenediamine, N-phenyl-para-phenylenediamine, 2-xcex2-hydroxyethyloxy-para-phenylenediamine, 2-xcex2-acetylaminoethyloxy-para-phenylenediamine and N-(xcex2-methoxyethyl)-para-phenylenediamine, and the acid addition salts thereof.
Among the para-phenylenediamines of formula (II) above, para-phenylenediamine, para-tolylenediamine, 2-isopropyl-para-phenylenediamine, 2-xcex2-hydroxyethyl-para-phenylenediamine, 2-xcex2-hydroxyethyloxy-para-phenylenediamine, 2,6-dimethyl-para-phenylenediamine, 2,6-diethyl-para-phenylenediamine, 2,3-dimethyl-para-phenylenediamine, N,N-bis(xcex2-hydroxyethyl)-para-phenylenediamine, 2-chloro-para-phenylenediamine and 2-xcex2-acetylaminoethyloxy-para-phenylenediamine, and the acid addition salts thereof, are most particularly preferred.
According to the invention, the term double bases is understood to refer to the compounds comprising at least two aromatic rings bearing amino and/or hydroxyl groups.
Among the double bases which can be used as oxidation bases in the dye compositions according to the invention, examples include the compounds corresponding to formula (IlI) below, and the acid addition salts thereof: 
wherein:
Z1 and Z2, which may be identical or different, are chosen from a hydroxyl radical and an xe2x80x94NH2 radical which may be substituted with a C1-C4 alkyl radical or with a linker arm G;
the linker arm G is chosen from linear alkylene chains comprising from 1 to 14 carbon atoms and branched alkylene chains comprising from 2 to 14 carbon atoms, wherein said chains may be interrupted by or terminated with at least one nitrogenous group and/or at least one hetero atom, such as oxygen, sulphur and nitrogen atoms, and optionally substituted with at least one radical chosen from hydroxyl and C1-C6 alkoxy radicals;
R22 and R23 are chosen from hydrogen and halogen atoms, C1-C4 alkyl radicals, C1-C4 monohydroxyalkyl radicals, C2-C4 polyhydroxyalkyl radicals, C1-C4 aminoalkyl radicals, and a linker arm G;
R24, R25, R26, R27, R28 and R29, which may be identical or different, are chosen from a hydrogen atom, a linker arm G and C1-C4 alkyl radicals;
with the proviso that the compounds of formula (III) contain only one linker arm G per molecule.
Among the nitrogenous groups of formula (III) above, examples include amino, mono(C1-C4)alkylamino, di(C1-C4)alkylamino, tri(C1-C4)alkylamino, monohydroxy(C1-C4)alkylamino, imidazolinium and ammonium radicals.
Among the double bases of formula (III) above, examples include N,Nxe2x80x2-bis(xcex2-hydroxyethyl)-N,Nxe2x80x2-bis(4xe2x80x2-aminophenyl)-1,3-diaminopropanol, N,Nxe2x80x2-bis(xcex2-hydroxyethyl)-N,Nxe2x80x2-bis(4xe2x80x2-aminophenyl)ethylenediamine, N,Nxe2x80x2-bis(4-aminophenyl)-tetramethylenediamine, N,Nxe2x80x2-bis(xcex2-hydroxyethyl)-N,Nxe2x80x2-bis(4-aminophenyl)-tetramethylenediamine, N,Nxe2x80x2-bis(4-methylaminophenyl)tetramethylenediamine, N,Nxe2x80x2-bis-(ethyl)-N,Nxe2x80x2-bis(4xe2x80x2-amino-3xe2x80x2-methylphenyl)ethylenediamine and 1,8-bis(2,5diaminophenoxy)-3,5-dioxaoctane, and the acid addition salts thereof.
Among these double bases of formula (III), N,Nxe2x80x2-bis(xcex2-hydroxyethyl)-N,Nxe2x80x2-bis(4xe2x80x2-aminophenyl)-1,3-diaminopropanol and 1,8-bis(2,5-diaminophenoxy)-3,5-dioxaoctane, or one of the acid addition salts thereof, are particularly preferred.
Among the para-aminophenols which can be used as oxidation bases in the dye compositions according to the invention, examples include the compounds corresponding to formula (IV) below, and the acid addition salts thereof: 
wherein:
R30 is chosen from hydrogen and halogen atoms, C1-C4 alkyl radicals, C1-C4 monohydroxyalkyl radicals, (C1-C4)alkoxy(C1-C4)alkyl radicals, C1-C4 aminoalkyl radicals, and hydroxy(C1-C4)alkylamino(C1-C4)alkyl radicals,
R31 is chosen from hydrogen and halogen atoms, C1-C4-alkyl radicals, C1-C4 monohydroxyalkyl radicals, C2-C4 polyhydroxyalkyl radicals, C1-C4 aminoalkyl radicals, C1-C4 cyanoalkyl radicals, and (C1-C4)alkoxy-(C1-C4)alkyl radicals,
with the proviso that at least one of the radicals R30 and R31 is a hydrogen atom.
Among the para-aminophenols of formula (IV) above, examples include para-aminophenol, 4-amino-3-methylphenol, 4-amino-3-fluorophenol, 4-amino-3-hydroxymethylphenol, 4-amino-2-methylphenol, 4-amino-2-hydroxymethylphenol, 4-amino-2-methoxymethylphenol, 4-amino-2-aminomethylphenol, 4-amino-2-(xcex2-hydroxyethylaminomethyl)phenol and 4-amino-2-fluorophenol, and the acid addition salts thereof.
Among the ortho-aminophenols which can be used as oxidation bases in the dye compositions according to the invention, examples include 2-aminophenol, 2-amino-5-methylphenol, 2-amino-6-methylphenol and 5-acetamido-2-aminophenol, and the acid addition salts thereof.
Among the heterocyclic bases which can be used as oxidation bases in the dye compositions according to the invention, examples include pyridines, pyrimidines and pyrazoles, and the acid addition salts thereof.
Among the pyridines, preferred compounds are described, for example, in patents GB 1,026,978 and GB 1,153,196 (the disclosures of which are specifically incorporated by reference herein), such as 2,5-diaminopyridine, 2-(4-methoxyphenyl)amino-3-aminopyridine, 2,3-diamino-6-methoxypyridine, 2-(xcex2-methoxyethyl)amino-3-amino-6-methoxypyridine and 3,4-diaminopyridine, and the acid addition salts thereof.
Among the pyrimidines, preferred compounds are described, for example, in German patent DE 2,359,399 or Japanese patents JP 88-169,571 and JP 91-10659 or patent application WO 96/15765 (the disclosures of which are specifically incorporated by reference herein), such as 2,4,5,6-tetraaminopyrimidine, 4-hydroxy-2,5,6-triaminopyrimidine, 2-hydroxy-4,5,6-triaminopyrimidine, 2,4-dihydroxy-5,6-diaminopyrimidine and 2,5,6-triaminopyrimidine, and pyrazolopyrimidine derivatives such as those mentioned in patent application FR-A-2,750,048 (the disclosure of which is specifically incorporated by reference herein), and examples include pyrazolo[1,5-a]pyrimidine-3,7-diamine; 2,5-dimethylpyrazolo[1,5-a]pyrimidine-3,7-diamine, pyrazolo[1,5-a]pyrimidine-3,5-diamine; 2,7-dimethylpyrazolo[1,5-a]pyrimidine-3,5-diamine, 3-aminopyrazolo[1,5-a]pyrimidin-7-ol; 3-aminopyrazolo[1,5-a]pyrimidin-5-ol; 2-(3-aminopyrazolo[1,5-a]pyrimidin-7-ylamino)ethanol, 2-(7-aminopyrazolo[1,5-a]pyrimidin-3-ylamino)ethanol, 2-[(3-aminopyrazolo[1,5-a]pyrimidin-7-yl)(2-hydroxyethyl)amino]ethanol, 2-[(7-aminopyrazolo[1,5-a]pyrimidin-3-yl)(2-hydroxyethyl)amino]ethanol, 5,6-dimethylpyrazolo[1,5-a]pyrimidine-3,7-diamine, 2,6-dimethylpyrazolo[1,5-a]pyrimidine-3,7-diamine and 2,5,N7,N7-tetramethylpyrazolo[1,5-a]pyrimidine-3,7-diamine and the addition salts and tautomeric forms thereof, when a tautomeric equilibrium exists, and the acid addition salts thereof.
Among the pyrazoles, preferred compounds are described in patents DE 3,843,892, DE 4,133,957 and patent applications WO 94/08969, WO 94/08970, FR-A-2,733,749 and DE 195 43 988 (the disclosures of which are specifically incorporated by reference herein), for example 4,5-diamino-1-methylpyrazole, 3,4-diaminopyrazole, 4,5-diamino-1-(4xe2x80x2-chlorobenzyl)pyrazole, 4,5-diamino-1,3-dimethylpyrazole, 4,5-diamino-3-methyl-1-phenylpyrazole, 4,5-diamino-1-methyl-3-phenylpyrazole, 4-amino-1,3-dimethyl-5-hydrazinopyrazole, 1-benzyl-4,5-diamino-3-methylpyrazole, 4,5-diamino-3-tert-butyl-1 -methylpyrazole, 4,5-diamino-1-tert-butyl-3-methylpyrazole, 4,5-diamino-1-(xcex2-hydroxyethyl)-3-methylpyrazole, 4,5-diamino-1-ethyl-3-methylpyrazole, 4,5-diamino-1-ethyl-3-(4xe2x80x2-methoxyphenyl)pyrazole, 4,5-diamino-1-ethyl-3-hydroxymethylpyrazole, 4,5-diamino-3-hydroxymethyl-1-methylpyrazole, 4,5-diamino-3-hydroxymethyl-1-isopropylpyrazole, 4,5-diamino-3-methyl-1-isopropylpyrazole, 4-amino-5-(2xe2x80x2-aminoethyl)amino-1,3-dimethylpyrazole, 3,4,5-triaminopyrazole, 1-methyl-3,4,5-triaminopyrazole, 3,5-diamino-1-methyl-4-methylaminopyrazole and 3,5-diamino-4-(xcex2-hydroxyethyl)amino-1-methylpyrazole, and the acid addition salts thereof.
The at least one oxidation base preferably is present in an amount ranging from about 0.0005 to about 12% by weight relative to the total weight of the dye composition according to the invention, and even more preferably from about 0.005 to about 6% by weight relative to this weight.
The preferred at least one cationic direct dye of formula (I) according to the invention is chosen from:
4xe2x80x2-dimethylaminophenyl-2-azopyridine N-oxide of formula: 
4xe2x80x2-dimethylamino-2xe2x80x2-methylphenyl-2-azopyridine N-oxide of formula: 
2-[(1,3-diamino-6-methyl-4-phenyl)azo]-3-methylbenzothiazolium iodide of formula: 
6xe2x80x2-hydroxybenzomorpholine-7xe2x80x2-aza-2-methyl-3-benzothiazolium chloride of formula: 
6xe2x80x2-hydroxybenzomorpholine-7xe2x80x2-aza-2-methyl-4-phenyl-3-thiazolium perchlorate of formula: 
6xe2x80x2-hydroxybenzomorpholine-7xe2x80x2-azo-2-diphenyl-3,4-thiazolium perchlorate of formula: 
6xe2x80x2-hydroxybenzomorpholine-7xe2x80x2-aza-2-methyl-3-benzothiazolium chloride of formula: 
6xe2x80x2-hydroxybenzomorpholine-7xe2x80x2-aza-2-methyl-4-phenyl-3-thiazolium perchlorate of formula: 
2xe2x80x2,4xe2x80x2-diamino-5xe2x80x2-methoxyphenyl-2-azopyridine N-oxide of formula: 
2xe2x80x2-acetamido-4xe2x80x2-hydroxy-5xe2x80x2-methylphenyl-2-azopyridine N-oxide of formula: 
2xe2x80x2-acetamido-4xe2x80x2-dimethylaminophenyl-2-azopyridine N-oxide of formula: 
2xe2x80x2-amino-4xe2x80x2-dimethylaminophenyl-2-azopyridine N-oxide of formula: 
2xe2x80x2,4xe2x80x2-diamino-5xe2x80x2-methylphenyl-2-azomethoxy-1-pyridinium perchlorate of formula: 
2xe2x80x2,5xe2x80x2-dimethyl-4xe2x80x2-hydroxyphenyl-2-azopyridine N-oxide of formula: 
2xe2x80x2-dimethylamino-4xe2x80x2-hydroxyphenyl-2-azopyridine N-oxide of formula: 
4xe2x80x2-dimethylamino-2xe2x80x2-hydroxyphenyl-2-azopyridine N-oxide of formula: 
3xe2x80x2,5xe2x80x2-dimethyl-4xe2x80x2-hydroxyphenyl-2-azopyridine N-oxide of formula: 
4xe2x80x2-dimethylamino-2xe2x80x2-nitrophenyl-2-azopyridine N-oxide of formula: 
8xe2x80x2-hydroxyquinoline-5xe2x80x2:2xe2x80x2-azopyridine N-oxide of formula: 
2xe2x80x2-nitro-4xe2x80x2-dimethylaminophenyl-2-azomethoxy-1-pyridinium methosulphate of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-5-nitropyridine N-oxide of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-6-methylpyridine N-oxide of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-5-methylpyridine N-oxide of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-3-methylpyridine N-oxide of formula: 
4xe2x80x2-diethylaminophenyl-2-azo-3-methylpyridine N-oxide of formula: 
4xe2x80x2-dimethylamino-2xe2x80x2-acetylaminophenyl-2-azo-3-methylpyridine N-oxide of formula: 
4xe2x80x2-aminonaphthalene-1xe2x80x2:2-azo-6-methylpyridine N-oxide of formula: 
4xe2x80x2-di(xcex2-hydroxyethyl)aminophenyl-2-azo-6-methylpyridine N-oxide of formula: 
4xe2x80x2-diethylaminophenyl-2-azo-6-methylpyridine N-oxide of formula: 
2xe2x80x2,5xe2x80x2-dimethyl-4xe2x80x2-hydroxyphenyl-2-azo-6-methylpyridine N-oxide of formula: 
4xe2x80x2-di(xcex2-hydroxyethyl)aminophenyl-2-azo-4-methylpyridine N-oxide of formula: 
4xe2x80x2-diethylaminophenyl-2-azo-4-methylpyridine N-oxide of formula: 
4xe2x80x2-aminonaphthalene-1xe2x80x2:2-azo-4-methylpyridine N-oxide of formula: 
2xe2x80x2,4xe2x80x2-diamino-5xe2x80x2-methylphenyl-2-azo-2-4-methylpyridine N-oxide of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-4-methylpyridine N-oxide of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-4,6-dimethylpyridine N-oxide of formula: 
2xe2x80x2,5xe2x80x2-dimethyl-4xe2x80x2-hydroxyphenyl-2-azo-4-methylpyridine N-oxide of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-5-chloropyridine N-oxide of formula: 
4xe2x80x2-dimethylamino-2xe2x80x2-methylphenyl-2-azo-5-chloropyridine N-oxide of formula: 
4xe2x80x2-diethylaminophenyl-2-azo-5-chloropyridine N-oxide of formula: 
6xe2x80x2-hydroxybenzomorpholine-7xe2x80x2:2-azopyridine N-oxide of formula: 
6xe2x80x2-hydroxybenzomorpholine-7xe2x80x2:2-azo-1-methoxypyridinium methosulphate of formula: 
2xe2x80x2,4xe2x80x2-diamino-5xe2x80x2-methylphenyl-2-azopyridine N-oxide of formula: 
2xe2x80x2-methyl-5xe2x80x2-oxo-4xe2x80x2-phenyidihydropyrazolyl-2-azo-1-methoxypyridinium methosulphate of formula: 
3xe2x80x2-methyl-2xe2x80x2,4xe2x80x2,6xe2x80x2-trioxohexahydropyrimidinyl-2-azopyridine N-oxide of formula: 
4xe2x80x2-aminophenyl-2-azopyridine N-oxide of formula: 
4xe2x80x2-di(xcex2-hydroxyethyl)aminophenyl-2-azopyridine N-oxide of formula: 
4xe2x80x2-(N-phenylamino)phenyl-2-azopyridine N-oxide of formula: 
4xe2x80x2-(N-phenylamino)phenyl-2-azo-3-methylpyridine N-oxide of formula: 
4xe2x80x2-aminophenyl-2-azo-1,3-dimethylpyridinium methosulphate of formula: 
4xe2x80x2-di(xcex2-hydroxyethyl)aminophenyl-2-azo-1,4-dimethylpyridinium methosulphate of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-1,3-dimethylpyridinium methosulphate of formula: 
4xe2x80x2-N-phenylaminophenyl-2-azo-1,6-dimethylpyridinium methosulphate of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-1,5-dimethylpyridinium methosulphate of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-1,6-dimethylpyridinium methosulphate of formula: 
2xe2x80x2,4xe2x80x2,6xe2x80x2-trioxohexahydropyrimidinyl-2-azopyridine N-oxide of formula: 
4xe2x80x2-dimethylaminophenyl-2-azo-1,3-dimethylbenzimidazolium perchlorate of formula: 
2xe2x80x2,4xe2x80x2-diamino-3xe2x80x2-pyridine-2-azopyridine N-oxide of formula: 
The at least one cationic direct dye of formula (I) used according to the invention preferably is present in an amount ranging from about 0.001 to about 10% by weight relative to the total weight of the dye composition, and even more preferably from about 0.01 to about 5% by weight relative to this weight.
The dye composition according to the invention may further comprise at least one coupler and/or at least one additional direct dye other than the compounds of formula (I), particularly to modify the shades or to enrich them with glints.
Among the couplers which can be present in the dye composition according to the invention, examples include meta-phenylenediamines, meta-aminophenols, meta-diphenols and heterocyclic couplers, and the addition salts thereof with an acid.
When they are present, the at least one coupler preferably is present in an amount ranging from about 0.0001 to about 10% by weight relative to the total weight of the dye composition, and even more preferably from about 0.005 to about 5% by weight relative to this weight.
In general, the preferred addition salts with an acid which can be used in the context of the dye compositions of the invention (oxidation bases and couplers) are the hydrochlorides, hydrobromides, sulphates, tartrates, lactates and acetates.
The medium suitable for dyeing (or support) for the dye composition according to the invention generally comprises water or a mixture of water and at least one organic solvent to dissolve the compounds which would not be sufficiently water-soluble. Examples include C1-C4 alkanols, such as ethanol and isopropanol, as organic solvents.
The solvents can be present in proportions preferably ranging from about 1 to about 40% by weight relative to the total weight of the dye composition, and even more preferably from about 5 to about 30% by weight.
The pH of the dye composition according to the invention generally ranges from about 3 to about 12, and preferably from about 5 to about 12. The pH can be adjusted to the desired value by means of acidifying or basifying agents usually used for dyeing keratin fibres.
Representative acidifying agents include organic or inorganic acids such as hydrochloric acid, orthophosphoric acid, sulphuric acid, carboxylic acids such as acetic acid, tartaric acid, citric acid and lactic acid, and sulphonic acids.
Representative basifying agents include aqueous ammonia, alkaline carbonates, alkanolamines such as mono-, di- and triethanolamine, 2-methyl-2-aminopropanol and derivatives thereof, sodium hydroxide, potassium hydroxide and the compounds of formula (IX) below: 
wherein W is a propylene residue optionally substituted with a hydroxyl group or a C1-C4 alkyl radical; R32, R33, R34 and R35, which may be identical or different, are chosen from a hydrogen atom and C1-C4 alkyl and C1-C4 hydroxyalkyl radicals.
The dye composition according to the invention can also contain various adjuvants conventionally used in compositions for dyeing the hair.
Needless to say, a person skilled in the art will take care to select this or these optional complementary compounds such that the advantageous properties intrinsically associated with the dye composition according to the invention are not, or are not substantially, adversely affected by the addition(s) envisaged.
The dye composition according to the invention can be in various forms, such as in the form of liquids, creams or gels, which may be pressurized, or in any other form suitable for dyeing keratin fibres, particularly human hair.
Another subject of the invention is a process for dyeing keratin fibres, especially human keratin fibres such as the hair, using the dye composition as defined above.
According to this process, the dye composition as defined above is applied to the fibres, the colour being developed at acidic, neutral or alkaline pH by means of an oxidizing agent added to the dye composition just at the time of use, or which is present in an oxidizing composition applied simultaneously or sequentially in a separate manner.
According to one particularly preferred embodiment of the dyeing process according to the invention, the dye composition described above is mixed, at the time of use, with an oxidizing composition containing, in a medium suitable for dyeing, at least one oxidizing agent present in an amount sufficient to develop a coloration. The mixture obtained is then applied to the keratin fibres and is left on the fibres for about 3 to about 50 minutes, preferably for about 5 to about 30 minutes, after which the fibres are rinsed, washed with shampoo, rinsed again and dried.
The oxidizing agent present in the oxidizing composition as defined above can be chosen from the oxidizing agents conventionally used for the oxidation dyeing of keratin fibres, such as, for example, hydrogen peroxide, urea peroxide, alkali metal bromates, persalts such as perborates and persulphates, peracids, and enzymes such as 2-electron oxidoreductases, peroxidases and lactases. Hydrogen peroxide is particularly preferred.
The pH of the oxidizing composition containing the oxidizing agent as defined above is such that, after mixing with the dye composition, the pH of the resulting composition applied to the keratin fibres preferably ranges from about 3 to about 12 and even more preferably from about 5 to about 11. The pH is adjusted to the desired value by means of acidifying or basifying agents usually used for dyeing keratin fibres and as defined above.
The oxidizing composition as defined above can also contain various adjuvants conventionally used in compositions for dyeing the hair.
The composition that is finally applied to the keratin fibres can be in various forms, such as in the form of liquids, creams or gels or in any other form suitable for dyeing keratin fibres, particularly human hair.
Another subject of the invention is a multi-compartment dyeing device or xe2x80x9ckitxe2x80x9d or any other multi-compartment packaging system, a first compartment comprising the dye composition as defined above and a second compartment comprising the oxidizing composition as defined above. These devices can be equipped with means for delivering the desired mixture onto the hair, such as the devices described in patent FR-2,586,913, in the name of the L""Orxc3xa9al, the disclosure of which is specifically incorporated by reference herein.